1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) apparatus, and more particularly to a light guide plate for improving a front visual angle characteristic and an LCD apparatus having the same.
2. Description of the Related Art
In general, an LCD apparatus has an advantage over a CRT type display apparatus in aspects of weight and size. The advantage of the LCD can be realized by using a liquid crystal. The liquid crystal is controlled by an electric field. The liquid crystal is arranged in a predetermined direction parallel to a direction of the electric field, and a light transmittance varies depending on the arrangement of the liquid crystal.
The LCD apparatus requires a light to display an image through the liquid crystal. That is, since display properties are varied depending on a uniformity of a light provided to the liquid crystal, the light having a uniform brightness has to be provided to the liquid crystal.
However, it is difficult to provide a surface light source having the uniform brightness to the liquid crystal. Thus, a lamp 10 having a linear light source or a light emitting diode (LED) having a point light source are used as a device that provides the light as shown in FIG. 1.
FIG. 1 is a schematic view showing an LCD panel of a conventional LCD apparatus. FIG. 2 is a graph showing a distribution of brightness in accordance with a visual angle in the LCD apparatus shown in FIG. 1.
Referring to FIG. 1, the light having the linear light source or the point light source is incident to a light guide plate 20, and then the light guide plate 20 converts the light having the linear or point light sources into a light having the surface light source.
After converting the linear light source into the surface light source by the light guide plate 20, the light is emitted through a light emitting surface of the light guide plate 20. However, since a refractive index of the light guide plate 20 is greater than that of an air, the light having the surface light source is emitted in a direction inclined, about 75 to 83 degrees, with respect to a direction perpendicular to a light emitting surface of the light guide plate 20. This means that the brightness of the front visual angle of the LCD having the light guide plate 20 is lowered, so that a quality of the displayed image is not desirable.
To prevent the brightness from being lowered, a diffusion sheet 30, a first prism sheet 43, a second prism sheet 46 are sequentially disposed on the light guide plate 20. The diffusion sheet 30, the first prism sheet 43 and the second prism sheet 46 change the direction of the light inclined with respect to a normal line to the light emitting surface into a direction perpendicular to the light emitting surface of the light guide plate 20.
The LCD apparatus further includes a reflecting plate 15 under the light guide plate 20, a protecting sheet 50 on the second prism sheet 46 and LCD panel 60 that controls the liquid crystal.
Referring to FIG. 2, a graph indicated by a character xe2x80x9caxe2x80x9d shows the brightness distribution of the light emitted through the light guide plate 20, a graph indicated by a character xe2x80x9cbxe2x80x9d shows the brightness distribution of the light sequentially emitted through the light guide plate 20 and the diffusion sheet 30, and a graph indicated by a character xe2x80x9ccxe2x80x9d shows the brightness distribution of the light sequentially emitted through the light guide plate 20, the diffusion sheet 30 and the first and second prism sheets 43 and 46.
With reference to the graph xe2x80x9caxe2x80x9d, in case of the light through the light guide plate 20, the brightness of the front visual angle is low and the brightness of the visual angle of about 70 to 80 degrees is maximized. The light emitted from the diffusion sheet 30 has the brightness of the front visual angle generally greater than that of the light emitted from the light guide plate 20, as indicated by the character xe2x80x9cbxe2x80x9d. The light emitted from the first and second prism sheets 43 and 46 has the highest brightness of the front visual angle as indicated by the character xe2x80x9ccxe2x80x9d. The light of which the direction thereof is corrected by the diffusion sheet 30, the first prism sheet 43 and the second prism sheet 46 is provided to the LCD panel, thereby displaying the image having a uniform brightness in general.
However, since the LCD apparatus adopts some sheets such as the diffusion sheet 30, the first and second sheets 43 and 46 and so on, the thickness and the weight of the LCD apparatus are increased. Also, the manufacturing cost of the LCD apparatus increases by adopting the diffusion sheet 30, the first and second sheets 43 and 46 and the like.
The present invention provides a light guide plate for improving a front visual angle characteristic.
The present invention provides an LCD apparatus having a reduced number of optical sheets.
The present invention provides an LCD apparatus without an optical sheet.
In one aspect of the invention, there is provided a light guide plate comprising: a side portion for receiving light; a light reflecting portion for reflecting the light input through the side portion; and a light emitting portion facing the light reflecting portion, for emitting the light reflected by the light reflecting portion, wherein the light emitting portion has a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion at a front visual angle.
In another aspect, there is provided an LCD apparatus comprising: an LCD panel assembly for controlling a liquid crystal to display an image; and a backlight assembly having a lamp assembly for supplying a light and a light guide plate for guiding the light from the lamp assembly to the LCD panel assembly, wherein the light guide plate comprises a side portion for receiving the light, a light reflecting portion for reflecting the light input through the side portion, and a light emitting portion facing he light reflecting portion, for emitting the light reflected by the light reflecting portion, the light emitting portion includes a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion at a front visual angle.
In further aspect, there is provided an LCD apparatus comprising: an LCD panel assembly for controlling a liquid crystal to display an image; and a backlight assembly having a lamp assembly for supplying a light, a light guide plate for guiding the light from the lamp assembly to the LCD panel assembly and a prism sheet disposed between the LCD panel and the light guide plate, wherein the light guide plate comprises a side portion for receiving the light, a light reflecting portion for reflecting the light input through the side portion, and a light emitting portion facing the light reflecting portion, for emitting the light reflected by the light reflecting portion, and the light emitting portion includes a visual angle correcting means for increasing a brightness of the light emitted through the light emitting portion a front visual angle.